US1885373A - Variable rheostat - Google Patents

Description

Nov. 1, 1932. R. B. PLANCHE 1,885,373

VARIABLE RHEOS'IAT Filed June 16, 1931 5 Sheets-Sheet 1 Nov. 1, 1932. R. a. PLANCHE 1,335,373

VARIABLE RHEOSTAT Filed Jun e 16, 1951 5 Sheets-Sheet 2 23 221819 "T 16 jg wz Nov. 1, 1932. R. B. PLANCHE VARIABLE RHEOSTAT Filed June 16. 1931 5 Sheets-Sheet I5 Nov. l, 1932. R. B. PLANCHE" VARIABLE RHEOSTAT Filed J%e 16. 1951 5 Sheets-Sheet 4 1932- R. B. PLANCHE VARIABLE RHEOSTAT I Filed June 16. 1931 5 Sheets-Sheet 5 Patented Nov. 1, 1932 UNITED STATES PATENT OFFICE VARIABLE RHEOSTAT Application filed June 16, 1931, Serial No. 544,872, and in France June 25, 1930.

while the liquid under the influence of the electric motor being started is automatically displaced to cover the said stationary electrodes to a greater or less extent in order to vary the resistance and finally cause it to be short circuited.

The invention is embodied in apparatus in which the displacement of the liquid inslde the casing surrounding the electrodes is obtained by a pump driven by the electric motor to be started, and which casing is provided at its upper part with channels for the return of liquid, and also embodies a flexible diaphragm for closing the channels and which on being raised causes through suitable mechanism the short circuiting of the electrodes which are connected to the motor.

The invention also includes other devices of particular interest as follows A stop valve for cutting off the supply of the liquid when the chamber is full and on the other hand to facilitate emptying.

marily when the rheostat is hot and to allow entrance of air when the vacuum becomes too great or vice versa the filling orifice of the casing is provided with an hydraulic valve.

2. To maintain the level of liquid in the casing uniformly constant a filling means from an auxiliary reservoir is provided arranged in the upper part of the apparatus and connnunicating with a tube prolonging the rheostat at the lower level of the liquid, through a spring valve operated by the filling valve of the auxiliary reservoir so that it is only open when this filling valve is completely closed.

3. In order to avoid the use of a packing gland at the outlet from the casing of the shaft of the lifting pump this outlet of the shaft is arranged prolonged above the upper level of the liquid either by means of a belt and pulley or gear drive or by arranging the turbine horizontally so that its shaft will be vertical.

4. To provide the first resistance on starting in cases where the level of the liquid is insufiicient and to rapidly warm this liquid to raise it as quickly as possible to its normal temperature and resistant quality for working, the lower ends of the electrodes are connected together by a wire or other electric resistance submerged in the liquid.

The invention will be fully understood on reference to the following description and the accompanying diagrammatic drawings which description and drawings are it mustbe understood only given by way of example.

In the drawings Fig. 1 is a section elevation on line 11 Figs. 2. and 3. I

Fig. 2 is a second sectional elevation at 90 to that shown in Fig. 1 on line 22 Figs. 1 and 3.

Fig. 3 is a sectional plan of the terminals and their short circuiting plan on line 33 Figs. 1 and 2.

Fig. 4 is a sectional elevation of a modification on line 4-4 Fig. 5.

Fig. 5 is a further section of the same modification on line 5-5 Fig. 6.

Fig. 6 is a View from above of the rheostat shown in Fig. 5, with the cover removed.

Fig. 7 shows in longitudinal elevation the arrangement of the hydraulic valve and the automatic filling.

Fig. 8 is a detail sectional view of the rheostat shown in Fig. 4. and embodying a construction permitting omission of the pressure packing f on the shaft of the turbine 8.

Fig. 9 shows diagrammatically the electrodes connected together at their lower ends by electrical resistances.

Fig. 10 is partly an elevation and partly a section of a modified form of the rheostat in which an auxiliary motor directly actuates the turbine.

Fig. 11 is a plan showing the rheostat connected to the motor controlled thereby.

Fig. 12 is a sectional view of a modified form of the invention.

,According to the invention the apparatus comprises a casing 1 having a plurality of compartments into which is allowed to flow through inlets 2 and 3 a predetermined quantity of conducting liquid to bring the level to a predetermined height. The liquid may be for example a solution of crystals of carbonate of soda or common salt dissolved in water.

Three metal plates 4:, 5, 6 electrically insulated from each other are mounted rigidly in the upper compartment 7 of the .casingl from which they are also insulated.

At one side of the base of the casing 1 provided a rotor having blades 8 enclosed in a casing 9. This rotor is keyed on to a shaft 10 and is rotated by a pulley 11 in one end thereof.

A packing gland 12 prevents the passage of liquid along the shaft. c

The three/plates 4, 5, 6 are provided with terminals 13 by which they are connected to the terminals of the motor to be started.

At the opposite side these same three plate are connected at 14 to three other terminals 15, 16, 17, arranged in the cover 18 of the casing but electrically insulated therefrom.

These last three terminals are provided below the cover with shoulders 19, 20, 21 and at the intersection of the lines joining their centres a metal plate 22 is mounted on a flexible insulating diaphragm 23 forming a fluid tight oint between the compartments 7 and 24: inside the cover 18.

This metal plate is held against the flexible diaphragm by a small spring 25.

Immediately under this diaphragm 23.,

(shown on the left hand side of Fig. 2) is.

a passage 26 which places the compartment 7 in communication with the lower reservoir 27 having an outlet plug 28.

The operation of the invention is as follows Suppose .it is desired .to start an electric motor.

For this purpose the aforesaid rheostat is mounted beside the electric motor and the shaft of said motor has mounted upon it a small pulley which drives, through a belt, the pulley 11 of the aforesaid starting resistance.

The terminals of the motor are connected with the terminals 13 of the rheostat.

A predetermined quantity of liquid is run through the plugs 2 or 3 until the ends of the electrodes 1, 5, 6 are partially submerged in the liquid (see Fig. 1)

If the circuit through the motor to be started isnow closed this latter commences to rotate slowly owing to the large resistance offered by the electrodes 4, 5, 6 which only dip a small distance into the liquid.

In rotating the motor rotates the pulley 11 and the rotor 8 through the shaft 10.

The liquid contained in the compartment 27 is raised by the centrifugal force developed by the rotor, due to its rotation, and the level of the liquid in the compartment 27 falls, while on the other hand it rises in the compartment 7 thus progressively immersing the resistance electrodes.

Due to this raising of the liquid the resistance is reduced and the motor speed increases until the liquid almost reaches the top of the compartment 7 and the compartment 27 is nearly empty. i

The resistance of the electrodes has then become very small, partly because they are almost completely submerged and partly because they are nearer to each other due to their submersion which reduces the relative resistance between them.

Theapparatus continuing to rotate causes the liquid to rise but at this moment it comes in Contact with the flexible diaphragm 23 which obstructs its passage.

The liquid therefore commences to overflow through the passage 26.

However this passage, although large enough for the escape of air, is not large enougi to allow the escape of all the liquid lifted by the pump 8 and hence the pressure 'of the liquid on the diaphragm rises and presses the ring22 upwardly into contact with the shoulders, 1.9, 20, 21 which thus short circuit the starting circuit of the motor.

At this moment the liquid circulation is continuing, a part escapes along the passage 26 and a further part is stopped in the pump itself due to the resistance which it meets.

A state of equilibrium is thus reached which maintained until the motor is running normally.

If an accidental breaking of the circuit is now supposed to occur, due to the opening of a switch or an electric contactor, for example, the motor stops and in proportion diminishes the speed of the rotor 8.

The centrifugal force due to the pump becomes insufiicient and the liquid contained in the chamber 7 escapes back to the reservoir through the periphery 29 of the pump.

Under the influence of the upper spring the short circuit is immediately broken, since the liquid level falls in the chamber 7, the resistance, increases again until the lower level-of the liquid is reestablished (the position shown in the drawings).

The apparatus is then ready for restarting.

In the modification shown in Figs. 4 6 the casing comprises two superposed sections 41 and a connected together at their centre. The pump 8 is placed in a trapezoidal shaped chamber carrying the lower section 41. This casing is also provided with holding down lugs 43.

The casing-of the pump is formed with holes the areas of which are carefully calculated.

The casing Z) on the left hand side of the pump 8 is provided with a regulating screw 0 which takes up the end play of the shaft, while the casing on the right hand side is formed in one with the end cap 6 closing the opening provided in the main casing for the insertion of the pump.

This same cap is provided with a small packing gland f necessary to preventloss of liquid.

The axis of the blades a of the pump is arranged in the centre of the main casing to give an even feed to the upper chamber.

The apparatus is provided with a control valve to prevent a too rapid rising of the liquid level. It comprises a member held against the bottom of the casing with a thick rubber joint 9. This member also carries a series of rectangular partitions which may be closed by a rubber sheet h.

A perforated bafile e is arranged below to prevent the rubber h from being deformed. This baffle also holds the rubber in place.

The operation of this controlling valve is as follows As soon as the pump 8 is started in operation the flow of liquid closes the rubber valve h and blocks the partitions 7c of the control valve entirely preventing the passage of water therethrough.

If on the other hand the pump stops and if the level of the liquid has risen in the upper chamber the pressure of the water opens this control valve and the water rapidly flows into the lower compartment through the large openings provided for this purpose.

Means for regulating the rise of liquid is provided for this arrangement.

It comprises a port Z, formed in the side wall of the pump casing. This port is controlled by a plug on which may be screwed more or less into the port Z.

A second plug a is provided to prevent loss of liquid during operation.

This arrangement of control may further be directly operated from outside the casing by replacing the second plug by a rod with a packing gland Fig. 12.

According to whether the rheostat is to be regulated once for all or according to need one or other of these arrangements will be adopted.

The filling valve Fig. 5 on the left hand side of the casing is provided with a filter 0 to prevent any foreign matter which might foul the apparatus from entering.

The plug p forms at the same time an indicator of the liquid level. It is provided for the purpose with a vertical rod (1 on which are marked the minimum and maximum levels. In order to be easily removable the plug is formed with a bayonet joint so that in order to ascertain the level it is only necessary to place the plug in position and remove it again without any screwing which mightvary the reading.

The electrodes 4, 5, 6 are formed triangular towards the bottom and rectangular towards the top as shown in Fig. 4 when viewed from the side and trapezoidal towards the base and rectangular towards the top when viewed from the front, see Fig. 5.

The combination of these shapes gives the following advantages.

1st. A large electrical resistance when the electrodes are only slightly immersed due to small area immersed and their relatively great distance apart.

2nd. Very small electrical resistance when they are completely immersed immediately before short cir .uit due to the fact of their large contact surface and their small distance apart.

They are further spaced equally apart and taken in section the distance which separates the two external electrodes from the lateral fl has of the upper compartment is half the distance which separates them from each other so that their electrical resistance remains constant.

That is to say if 4, 5, 6 are the electrodes above referred to the distance between 6 and e is identical with that between 4: and 5 and that etween 5 and 6, the electrical circuit being closed through the casing from which the electrodes are only separated by twice th half distance between each other, that is by the same distance.

At their upper ends these electrodes carry two metallic conducting studs y, welded, screwed or riveted thereto which act as the terminals.

The short circuiting arrangement comprises a diaphragm of rubber or similar elastic material, leather or the like. This joint is held in place by insulation 9" screwed into the cover.

The rubber diaphragm also forms a fluid tight joint.

Inside this insulation 1" a large port is provided which is closed by a metal plate 8 of parallel piped in shape towards its base and then rectangular, on which is screwed a leather disc t of the shape shown in Fig. 5.

he plate 8 is provided with two studs in and 4) which slide in an insulation member to carried inside the cover.

Copper conductors a0 connect the two rods y affixed to the electrodes.

The insulation 10 is shaped to serve at the same time to insulate the copper conductors a: connecting the electrodes together.

The operation of the short circuiting arrangement is as follows lVhen the liquid reaches the upper level the pressure raises the elastic diaphragm 23 which raises in its turn the metal plate 8 the upper part of which comes in contact with the three copper conductors connected respectively to the three electrodes to short ciri seen that if evaporation occurs and'the rheocuit them.

The bent shape of the copper conductors ences of level there may be. Further the sliding of the studs 24 and '0 in the insulation prevents this from tipping sideways and therefore keeps it horizontal.

- The casing is provided with cover plate 36 having a control knob 37 which may for example be similar to the plug employed for the filling valve. This cover plate is formed with three apertures 38 of any desired shape for the passage of the conducting leads 39.

In the modification shown in Fig. 7 the filling valve in the casing is formed with a tube A dipping into the liquid when this latter after having been raised by the pump is in the upper chamber of the rheostat. This tube further dips into a small reservoir B which remains constantly full of liquid even when the rheostat is working that is to say when the level is falling (Fig. 1).

This arrangement prevents the evaporation of the liquid when the rheostat is hot, that is to say when it has been working for some time or when the surrounding temperature is very high.

This hydraulic valve also permits the apparatus to breathe, that is to say to allow air to enter when the vacuum becomes too great or conversely to allow it to escape when the pressure exceeds a predetermined limit.

In order to condense as far as possible the vapour produced, the upper part of the tube A is mounted in a hollow cylinder C forming a condenser. The space C is maintained at a lower temperature than that of the rheostat since it is at about the surrounding temperatureywhile the rheostat must be at a higher temperature than the surrounding temperature due to the transformation of the electrical energy intoheat. This cylinder is formed at its upper end with vents D to permit the escape or entry of ir to the rheostat. A filling arrangement is provided to provide for keeping the level of theliquid in the rheostat absolutely constant.

This arrangement consists in forming the cover E as a reservoir for liquid.

At one side the cover is formed with a filling plug F which when it is screwed down causes a rod G to open a. small valve H allowing liquid to flow from the bottom of the reservoir forming the cover. I

This cover being in place it flows through a tube K which extends into the rheostat to the lower level of the liquid that is to say to the level taken by the liquid in the lower chamber when the pump has entirely filled the upper chamber. A oint J prevents leakage of the liquid.

If the upper reservoir in the cover is kept .fluid tight, that is to say, if the filling plug :gives a good contact whatever small differ F has been screwed down to prevent escape of liquid from the reservoir, it will be readily stat loses water, air rising up the tube K allows the liquid inthe reservoir to flow in sufficient quantity to re-establish the level exactly as in the case of known drinking troughs particularly used for birds. I

The function of the valve H provided in the base of the cover forming the reservoir is to prevent during filling of the reservoir E, that is to say when the plug F has been withdrawn, water from this reservoir being able to escape into the rheostat and so altering the level. This will not occur when the plug F is replaced and the fiuid tightness of the reservoir is reattained and the valve H is opened again and the water can recommence to how until stable conditions are again set The small quantity which escapes in this way has no appreciable eii'ect on the operation of the rheostat.

Further to allow for the discarding of a packing gland f as described above the pump shaft may be driven by a belt passing over a pulley M arranged as shown in Fig. 8, in an auxiliary casing Nto enable the shaft 0 to pass through the casing above the maximum liquid level and so avoid any leakage.

As shown in Fig. 9 the electrodes 4, 5, 6 may be connected together at their lower ends by a resistance wire such as R R .3 all three arranged in the same horizontal plane and immersed in the liquid in order.

1. To serve first as a starting resistance if the liquid level is low.

2. To rapidly heat the liquid in contact with this resistance to bring it as quickly possible to its normal temperature and resistant quality.

Lastly as shown in Fig. 10 the drive of the small pump 8 may be carried out by a small auxiliary motor l? receiving current either from the stator of the motor to be started or from the rotor.

It is preferable to employ in this class of rheostat a non-congelable electrolite and one only having a small variation in intrinsic powers of resistance during the raising of its temperature to normal. An electrolite which may be advantageously formed by a heat insulating liquid such as glycerine to which more or less water has been added or other liquid held in suspension or dissolved a conducting powder such as graphite or suitable mineral salts.

As will be understood and as a result of what has preceded the present invention is not limited either to the examples given above or to their different parts but includes on thecontrary all modifications and more especially n as the casing at a point above the level of the upper liquid the plane of rotation being horizontal and the shaft vertical.

What ll claim as my invention and desire to prot ct by Letters Patent is 1. An automatic rheostat for starting electric motors comprising the combination with stationary resistance electrodes of a casing containing conducting liquid compartments within the casing within one of which the electrodes are mounted a pump driven by the motor to be start-ed housed within a second compartment to pump liquid into the electrode compartment to progressively immerse the electrodes to a greater extent and means for finally short circuiting the resistance electrodes.

2. An automatic rheostat for starting electric motors comprising the combination with stationary resistance electrodes of a casing containing conducting liquid compartments within th casing within one of which the electrodes are mounted, a pump driven by the motor to be started, housed within a second compartment to pump liquid into the electrode compartment to progressively immerse the electrodes to a greater extent, a flexible diaphragm across the top of the electrode compartment and a contact maker carried by the diaphragm to short circuit the electrodes when the pressure of the liquid in the chamber reaches predetermined value.

3. An automatic rheostat :tor starting electric motors comprising the combination with stationary resistance electrodes of a casing containing conducting liquid compartments within the casing within one of which the electrodes are mounted, a pump driven by the motor to be started housed within a second compartment to pump liquid into the electrode compartment to progressively immerse the electrodes to a greater extent, a flexible diaphragm across the top of the electrode compartment, a contact maker carried by the diaphragm to short circuit the electrodes when the pressure of the liquid in the chamher reaches a predetermined value, means for allowing excess of liquid to return to the lower compartment and means to prevent the liquid level from rising too quickly.

4. An automatic rheostat for starting electric motors comprising the combination with stationary resistance electrodes of a casing containing conducting liquid compartments within the casing within one of which the electrodes are mounted a pump driven by the motor to be started housed within a second compartment to pump liquid into the electrode compartment to progressively immerse the electrodes to a greater extent, a flexible diaphragm across the top of the electrode compartment, a contact maker carried by the diaphragm to short circuit the electrodes when the pressure of the liquid in the chamber reaches a predetermined value, means for allowing excess of liquid to return to the lower compartment and a plug to control the outlet volume from the pump.

5. An automatic rheostat for starting electric motors, comprising the combination with stable resistance electrodes of a receptacle containing a liquid, compartments on each side or": this receptacle in each of which the electrodes are mounted, means actuated by the motor to be started contained in a second compartment for releasing the fluid in the compartment of the electrode, so as to progressively immerse the electrodes and means for finally short circuiting them, and an auxiliary reservoir for making up any loss of liquid.

6. An automatic rheostat for starting electric motors comprising the combination with stationary resistance electrodes of a fluid containing casing, compartments within the easing within one of which the electrodes are mounted, means driven by the motor to be started, housed within a second compartment to lift the fluid into the electrode compartment to progressively immerse the electrodes to a greater extent, an auxiliary reservoir for making up any loss or liquid, means for automatically allowing the making up liquid to flow into the lower compartment, and means for finally short circuiting the resistance electrodes.

7. An automatic rheostat for starting electro-motors as in claim 6 having, a valve on the outlet from the reservoir, and a tube connected thereto extending to the normal level of the liquid in the lower compartment.

In witness whereof I afiix my signature.

RENE BENJAMIN PLANOHE.

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